Recently, biometric authentication techniques have been developed to make contactless (or non-contact) authentication of a system user, based on an biometric image representing biometric information such as a vein pattern of a hand or finger, a fingerprint, a palmprint, or the like. A biometric authentication apparatus utilizing the biometric authentication technique collates an input biometric image representing the user's biometric information with registered biometric information representing a biometric image of a registered user registered in advance. In a case in which the input biometric information and the registered biometric information match as a result of the collating process, the biometric authentication apparatus authenticates the user as a legitimate user (that is, the registered user) who is authorized to use the system, and permits the authenticated user to use the system. For example, the biometric authentication apparatus may be built into the system, or may be externally connected to the system.
The biometric authentication apparatus is being utilized in various fields, such as log-on management to a personal computer, identity verification in an ATM (Automated Teller Machine) of a bank, access management to an office, or the like, for example. In addition, there are demands to reduce the size of the biometric authentication apparatus in order to expand the range in which the biometric authentication apparatus may be applied.
In order for the biometric authentication apparatus to authenticate the user with a high accuracy, it is desirable that a feature configuration of the biometric information clearly appears on the biometric image. For this reason, a sensor used in the biometric authentication apparatus to generate the biometric image may be provided with an illuminating optical system that irradiates illumination light on a capturing target such as the user's hand, in addition to an imaging optical system that captures the biometric information of the capturing target such as the user's hand using an imaging lens and an imaging device such as a CCD (Charged Coupled Device).
For example, Japanese Laid-Open Patent Publications No. 2009-031903 and No. 2013-130981 and Japanese National Publication of International Patent Application No. 2005-527874 propose a biometric authentication technique using the illuminating optical system and the imaging optical system. On the other hand, in order to expand the range in which the biometric authentication apparatus may be applied, it is desirable to reduce power consumption of the biometric authentication apparatus by considering a case in which the biometric authentication apparatus is driven by a battery, for example, in addition to satisfying the demands to reduce the size of the authentication apparatus.
For example, Japanese Laid-Open Patent Publication No. 2009-031903 proposes a thin type biometric authentication apparatus that acquires the biometric information, using an optical system integrally having the imaging optical system and the illuminating optical system that has a size approximately equal to or greater than the capturing target such as the finger to be authenticated. According to this proposed biometric authentication apparatus, the power consumption may be reduced because an illuminating range is controlled according to a capturing range of the biometric image. However, in a case in which the capturing target is a biometric part, such as the palm, that is large compared to the finger, for example, the illuminating optical system becomes large and it is difficult to reduce the size of the illuminating optical system.
On the other hand, Japanese Laid-Open Patent Publication No. 2013-130981 proposes a biometric authentication apparatus configured to sandwich the biometric part between the imaging optical system and the illuminating optical system that has the size approximately equal to or greater than the capturing target such as the finger to be authenticated. According to this proposed biometric authentication part, the power consumption may be reduced because the illuminating range is controlled according to the capturing range of the biometric image. However, in the case in which the capturing target is the biometric part, such as the palm, that is large compared to the finger, for example, the illuminating optical system becomes large and it is difficult to reduce the size of the illuminating optical system, as in the case of the biometric authentication apparatus proposed in Japanese Laid-Open Patent Publication No. 2009-031903.
In the conventional biometric authentication apparatuses provided with the illumination device, including the proposed biometric authentication apparatuses described above and biometric sensors, the illumination device and the biometric authentication apparatus become large and it is difficult to reduce the size of the illumination device and the biometric authentication apparatus in the case in which the biometric part that is the capturing target is large compared to the illuminating optical system of the illumination device.